I replaced the water pump in my 2000 BF50, and couldn't help but notice a lot of water coming out the cavity drain holes in the lower leg. It seems odd to me that water would be coming out these holes. I've never noticed that before, but then, I've never had this one apart before, and didn't pay much attention when running on the muffs.

The water pump, however, doesn't have a seal on the top cover where the shaft comes out. Presumably the impeller is the seal, up inside the metal 'basket' it runs in, like the metal plate on the bottom. Except that there are gaskets and an o-ring for the lower housing to the aluminium casting, where the bearings are. And gaskets between the pieces. But no seal for the shaft at the top, either in the parts book, or in the new cover, or the old covers.

Does this seem normal to everyone? Anyone ever change the impeller in a BF50? I can't find an answer on the web, nor on youtube vids.

So I made my own short video, showing the water peeing out the drain holes on the sides, and in front. Just doesn't seem right, though I'm no OB mechanic.

And some poor video, but it should give you an idea of the amount of water coming out those holes.

Tom
I know some O/B have an O-Ring that goes on the drive gear shaft & u slide it down the shaft until it sits on top of the water pump housing & some have an O-Ring that also goes into a slot on the shaft near the top just below the splines where the shaft slides into the engine
hope this helps

I'm actually in the process of changing the pump on our 97 BF50 today. You are right that there is no independent seal on the top of the pump housing. There is a tight fitting lip on the housing with veins below cast into the housing that may act as a seal. I've never used the muffs on our motor. I've always just run it in a barrel of water, but I do not recall ever seeing that much water leaking from the drain holes. Hopefully I will have everything re-assembled tomorrow and can let you know the results. I'm just waiting on the upgraded indicator fitting and hose to arrive along with a couple replacement bolts for the lower unit... I'll post more on that dilemma later.

From the picture, those holes look like they would normally be below water level, so you would not normally see water coming from them, water would flow into them until the motor starts (?)

Is the bearing on top a conventional steel bearing, with roller/balls and races, or a sleeve/ bush? If of corrosion resistant material it might be that the water going through that bearing is designed to cool and lubricate it, and then on the way out cools the exhaust tube below (?). All guesses, I'm not at all familiar with that motor, the flow volume does seem excessive as you say. (But would like to know the answer when you do find out just the same, lol).

I thought of the tube, but the pee stream is very strong, and under significant pressure. And it's rigid, and in the right place (measured X, Y, and Z relative to the interface plane). I thought maybe the rubber bushing at the top, where it plugs into the power head, is cracked, but I saw no signs of that. But it is possible.

The tube and the (new) bottom rubber bushing overlap a little over 1", so if I missed completely, no water would be pumped through the engine, especially not at the high pressure that's coming out of the pee hole. In the first two vids segments (takes? scenes?), it's a little wimpy, but that's due to lake slime film in the engine, which dries and has to work its way out a little at a time, partially clogging the fitting every time. But after a while, it stops doing that, and the stream is vigorous, as in the last part of the video (youtube editing, so kind of abrupt transitions ).

And you're right, seahouse; that joint is below the water line, by a fair amount. That puts the water pump, and the shift linkage bellows (which I replaced; you can just see the grease where the rod comes out), and the holes, below water.

The top bearing of the shaft, where it exits the lower leg, is below the water pump, and there are two lip seals, back to back, and facing up. To keep water out of the lower unit.

Last edited by Tomfoolery on Wed Jun 01, 2016 3:19 pm, edited 1 time in total.

Yes, #9 (water tube lower bushing) is new. As is the housing (including the bottom, which usually is not part of a kit), all gaskets, o-rings, seals, etc.

New thermostat, too, though that has nothing to do with the pump.

Or does it?

It didn't pass much water through those vent holes when I fired it up this spring. I think I posted a pic of that here a couple of weeks ago, in fact. The thermostat was stuck open, which I noticed because the pee stream was cold, and it usually warms rather quickly.

Perhaps when the thermostat is closed, the resistance to flow is greater, causing high bypass rates around the drive shaft. When it was stuck open, the engine wouldn't warm up (pee stream remained cold), and possibly presented less flow resistance.

I'm liking the back pressure from closed thermostat theory. You put it all back new and others confirm the shaft clearance at pump housing. Tattletale stream looks like you've got water up top. Did you notice the new gasket being thicker than the old one? The only left field theory I can come up with is the impeller to volute clearance is wider allowing leakage past the impeller toward the shaft.

I like your thermostat theory better. Back pressure would increase leakage even if the clearances didn't change...

I'm glad you're posting this thread Tom! I've just ordered an impeller kit for my Suzi DF60, and should be into what you are doing next week. On my first trip late last year I had no tell tale stream and resorted to closely monitoring the engine temperature in case I had to abort to a marina. Luckily the flow resumed and nothing overheated. It could have been a block or a worn and deformed impeller due to the previous severe winter, but I resolved to install a kit for this year's activities as it's a 2010 unit and never been done before. Wish me luck!

Crikey wrote:On my first trip late last year I had no tell tale stream and resorted to closely monitoring the engine temperature in case I had to abort to a marina. Luckily the flow resumed and nothing overheated. It could have been a block or a worn and deformed impeller due to the previous severe winter, but I resolved to install a kit for this year's activities as it's a 2010 unit and never been done before. Wish me luck!

I think my intermittent and/or weak stream was due to lake slime that dries inside the engine. Every spring, I have to poke out the hole with a paperclip, wiggle the hose a bit, and so on. But after a while it stops clogging. But an old impeller should probably be replaced anyway, as if the lobes start coming off, they'll get into the engine and really cause a problem. When I got my last boat (Yanmar diesel), first thing I did was pull the impeller, and several lobes were hanging on by a thread. Could have been bad.

I found a couple of youtube videos with Suzuki how-to's, and it looks even easier than the Honda. The Suz's have a shift rod that appears to be splined, rather than the threaded push-pull rod which requires tiny fingers to spin the coupler nut on and off. The pump looks similar (I suppose they're all somewhat similar), and it too looks like there's no seal where the shaft exits the top of the housing.

And don't forget that little bolt under the trim tab. I didn't know it was there initially, and was scratching my head as to why the cases opened a little at the front, but not at the rear. Doh!